DESCRIPTION: The proposed research seeks to clarify neural and/or neuropharmacological mechanisms regulating postnatal ocular growth and influencing the development of refractive errors, particularly myopia (nearsightedness). In chick and mammals including man, vision-dependent feedback mechanisms influence postnatal ocular growth, hence implicating neural mechanisms in the control of refraction. Much evidence identifies the retina itself as exerting a prominent influence on eye growth and refraction. In the retina of eyes with experimental myopia, the PI and others following the leads are finding neurochemical perturbations that are beginning to identify neural mechanisms regulating the growth process. The PI also has found a neural pathway through the ciliary ganglion influencing the equatorial expansion of the eye and proposes that the retina and other neural pathways interact in integrating the overall size, form and refraction of the growing eye. He seeks understanding of how these neural mechanisms interact and influence postnatal ocular growth and refractive status. Using the chick as a model, studies will be directed toward the following specific aims: 1) further definition of the role of retinal dopamine in ocular growth and the development of refractive errors; 2) clarification of cholinergic mechanisms modulating eye growth; 3) evaluation of other neuropharmacological mechanisms influencing ocular growth and refraction; and 4) identification of neural mechanisms controlling the shape of the eye and its components, as distinct from axial length and refraction alone. The PI hopes that these studies ultimately will lead to a sufficiently improved understanding of human refractive errors that rational approaches can be developed to prevent them.